FR2876380A1 - CHEMICAL SENSORS COMPRISING ANILINE POLYSILOXANES AS SENSITIVE MATERIALS AND THEIR USE FOR THE DETECTION OR DETERMINATION OF NITROUS COMPOUNDS - Google Patents

Abstract

The invention relates to chemical sensors comprising anilinated polysiloxanes as sensitive materials, and to their use for detecting or measuring nitro compounds, in particular nitroaromatics. Fields of application: explosives detection, control and monitoring atmospheric pollution and the quality of more or less confined environments, monitoring of industrial sites.

Description

CHEMICAL SENSORS COMPRISING POLYSILOXANES

  ANILINES AS SENSITIVE MATERIALS AND THEIR USE

  FOR THE DETECTION OR DETERMINATION OF NITROUS COMPOUNDS

DESCRIPTION TECHNICAL FIELD

  The present invention relates to chemical sensors comprising aniline polysiloxanes as sensitive materials and to the use of these sensors for detecting or measuring nitro compounds, in particular nitroaromatic compounds such as nitrobenzene (NB), dinitrobenzene (DNB), trinitrobenzene (TNB), nitrotoluene (NT), dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT) and the like.

  Such sensors are useful for the detection of explosives, whether to ensure the safety of public places such as airports, to control the lawfulness of goods in circulation on a territory, to fight against terrorism, to disarmament operations, to locate antipersonnel mines or to clear industrial or military sites.

  They are also environmental protection, in control and atmospheric monitoring and the quality of more or less confined environments, as well as for monitoring for safety purposes, industrial sites manufacturing, storing and / or handling nitro compounds .

  Useful for the particular case of pollution 2 STATE OF THE PRIOR ART The detection of explosives is a problem of crucial interest, particularly in terms of civil security.

  At present, several methods are used to detect vapors of nitro compounds in the constitution of explosives, such as the use of dogs "sniffers" trained and trained for this purpose, the laboratory analysis, for example by chromatography coupled with a mass spectrometer or an electron capture detector, samples taken on site, or infrared detection.

  These methods generally demonstrate a high sensitivity, which is essential for the detection of explosives given the very low concentration of vapors of nitro compounds that prevails in the vicinity of an explosive. However, they do not give complete satisfaction.

  Thus, the use of "sniffer" dogs has the disadvantage of requiring a long training of the dogs and their masters and being unsuitable for prolonged operations because of the limited attention span of the dogs.

  As for the other methods, the size of the equipment they use, their energy consumption and their implementation costs preclude the development of easily transportable and autonomous detection systems and, therefore, suitable for use on any type of sites.

  In recent years, the development of sensors able to detect in real time gaseous chemical species is in full swing. The operation of these sensors is based on the use of a film of a sensitive material, that is to say of a material of which at least one physical property P (mass, temperature, electrical conductivity, absorbance, fluorescence , ...) is modified in contact with the desired gas molecules, which has a system able to measure in real time any variation of this physical property and thus highlight the presence of the desired gas molecules.

  The advantages of chemical sensors over the aforementioned methods are many. instantaneous results, possibility of miniaturization and, therefore, portability, maneuverability and significant autonomy, low manufacturing and operating costs, etc. However, it is obvious that their performance is extremely variable depending on the nature of the sensitive material used.

  For the detection of gaseous nitro compounds, and more particularly of nitroaromatic compounds, many sensitive materials have already been proposed, among which mention may be made of porous silicon, vegetable charcoal, polyethylene glycol, amines, cyclodextrins and cavitands. and fluorescent compounds.

  It has also been proposed by Briglin et al. in Proceedings of SPIE, vol. 4394, 2001, 912-921, [1] to use, to detect dinitrotoluene, composites consisting of carbon black and poly [bis (cyanoallyl) siloxane] and carbon black and polymethyloctadecylsiloxane in a multisensor based system. on the measurement of a variation of the electrical conductivity of these composites.

  In addition, McGill et al. described in Sens. Actuators B65, 5-9, 2000, [2], and in the international application PCT WO-A-02/08314 [3], the detection of some nitroaromatic compounds (nitrobenzene, dinitrotoluene, trinitrotoluene) by a surface wave sensor comprising functionalized polysiloxanes as sensitive materials. These polysiloxanes are functionalized with a phenyl group substituted with one or more hexafluoroisopropanol (HFIP) groups.

  According to McGill et al., The presence of this HFIP group or groups is directly responsible for the sensitivity of the sensor to nitroaromatic compounds because it allows the formation of hydrogen bonds between the hydroxyl function present in these groups and the nitro group. nitroaromatic compounds.

  However, in the context of their work on the development of sensors intended more specifically to detect explosives, the inventors have found that sensors using as sensitive materials, polymers based on siloxanes functionalized with a phenyl group substituted by one or more functions amines (primary, secondary and / or tertiary) detect nitro compounds, and in particular nitroaromatic compounds, with a significantly higher sensitivity than sensors using the polysiloxanes recommended by McGill et al., including in the case where this phenyl group does not have a HFIP group during.

  And it is this observation which is the basis of the invention.

  DISCLOSURE OF THE INVENTION The subject of the invention is a chemical sensor which comprises, as sensitive material, at least one polymer comprising a siloxane repeating unit of formula (I) below: in which: X and Y represent, independently of each other, a single bond or a linear, branched or cyclic, saturated or unsaturated hydrocarbon group comprising from 1 to 30 carbon atoms and optionally one or more heteroatoms and / or one or more chemical functions comprising at least one minus one heteroatom and / or one or more aromatic or heteroaromatic groups; R 1 represents an aniline group corresponding to formula (II) below: (I) in which: Q represents a single bond, a -CH 2 - group, or a -NR 3 - group in which R 3 represents an atom of hydrogen or a linear hydrocarbon group, saturated or unsaturated, and comprising from 1 to 10 carbon atoms; R 4 to R 8 represent, independently of one another, a hydrogen atom, a chemical function comprising at least one heteroatom, or a linear, branched or cyclic hydrocarbon group, saturated or unsaturated, comprising from 1 to 30 carbon atoms and optionally one or more heteroatoms and / or one or more chemical functions comprising at least one heteroatom and / or one or more aromatic or heteroaromatic groups; and wherein, when Q is a single bond or a -CH 2 - group, then at least one of R 4 to R 8 is -NR 9 R 10 amine in which R 9 and R 10 are, independently of one another, a hydrogen atom, a chemical function comprising at least one heteroatom, or a linear, branched or cyclic hydrocarbon group, saturated or unsaturated, comprising from 1 to 30 carbon atoms and optionally one or more heteroatoms and / or one or more chemical functions comprising at least one heteroatom and / or one or more aromatic or heteroaromatic groups; R2 represents a hydrogen atom or an aniline group of formula (II) as defined above.

  In formula (I) above, when X and / or Y represent a single bond, then R1 and / or R2 are directly bonded to the silicon atom by a covalent bond.

  Similarly, when R 1 represents a group of formula (II) in which Q is a single bond, then the phenyl ring of this group is directly attached to x or to the silicon atom if X is itself a single bond , while, when R2 represents a group of formula (II) in which Q is a single bond, then the phenyl ring of this group is directly bonded to y or to the silicon atom if Y itself represents a single bond .

  On the other hand, when X and / or Y represent a hydrocarbon group comprising at least two carbon atoms and this group comprises one or more heteroatoms and / or one or more chemical functions and / or one or more aromatic or heteroaromatic groups, then this (these) heteroatom (s), this (these) chemical function (s) and aromatic (s) or heteroaromatic (s) group (s) may form a bridge within this group or be carried laterally by it, whereas, when R1, R2, R3, R4, R5, R6, R7, R9, R9, R10, R'1 and / or R12 represent a hydrocarbon group comprising at least two carbon atoms and that group contains one or more heteroatoms and / or one or more chemical functions and / or one or more aromatic or heteroaromatic groups, then this (these) heteroatom (s), this (these) chemical function (s) and that ( s) Aromatic group (s) or heteroaromatic (s) can form bridge within this group, be in. laterally by him or be at the end.

  According to the invention, the hydrocarbon group (s) falling within the formulas (I) and (II) above, when they are cyclic and unsaturated, may as well be aromatic groups (or heteroaromatic groups if they contain one or several heteroatoms in their ring or in one of their constituent rings), than non-aromatic groups (cycloalkenic or cycloalkynic).

  By way of examples of aromatic groups which may be used in the invention, mention may be made of the cyclopentadienyl, phenyl, benzyl, biphenyl, phenylacetylenyl, pyrene or anthracene groups, whereas, by way of examples of heteroaromatic groups, there may be mentioned mention may be made of furanyl, pyrrolyl, thiophenyl, oxazolyl, pyrazolyl, thiazolyl, imidazolyl, triazolyl, pyridinyl, pyranyl, quinolinyl, pyrazinyl and pyrimidinyl groups.

  The heteroatom (s) may be any atom other than carbon or hydrogen, for example an oxygen, sulfur, nitrogen, fluorine, chlorine, phosphorus, boron or silicon atom, the oxygen, sulfur and nitrogen atoms being preferred.

  The chemical function (s) comprising at least one heteroatom may in particular be chosen from the functional groups -OOOH, -COOR11r -CHO, -CO-, OH, -OR11, -SH, -SR11, -SO2R11, -NH2, -NHR11r -NR11R12 , -CONH2, -CONHR11r-CONR11R12, -C (Hal) 2, -OC (Hal) 2, -C (O) Hal, -CN, -COOCHO and -COOCOR11r in which: R11 represents a linear hydrocarbon group, branched or cyclic, saturated or unsaturated, comprising from 1 to 30 carbon atoms, or a covalent bond in the case where said chemical function forms a bridge in a C2 to Cao hydrocarbon group; R 12 represents a hydrocarbon group, linear, branched or cyclic, saturated or unsaturated, comprising from 1 to 30 carbon atoms, this group may be identical to or different from the hydrocarbon group represented by R 11; while Hal represents a halogen atom, for example a fluorine, chlorine or bromine atom.

  According to a first preferred embodiment of the invention, the siloxane repeating unit corresponds to formula (I) in which R 1 represents an aniline group of formula (IIa), (IIb) or (IIc) below:

NH -> NH2 (IIb)

NH

  In the formulas (IIb) and (IIc), the primary amine group of the aniline group may be in the ortho, meta or para position with respect to the element to which the phenyl ring is attached, that is to say, in the case of formula (IIb), with respect to the secondary amine group of this aniline group and, in the case of formula (IIc), with respect to x or to the silicon atom if X represents a single bond.

  According to another preferred embodiment of the invention, the siloxane repeating unit corresponds to formula (I) in which X represents an alkylene group comprising from 1 to 10 carbon atoms and, preferably, a propylene group, Y represents an alkylene group comprising 1 to 3 carbon atoms and, preferably, a methylene group, while R2 represents a hydrogen atom.

  Thus, among the siloxane repeating units of formula (I), those in which X represents a propylene group, R 1 represents an aniline group of formula (IIa), (IIb) or (IIc), Y represents a methylene group, are especially preferred. while R2 represents a hydrogen atom, and among them, those corresponding to formulas (Ia), (Ib) or (Ic) below:

NH (la) NH2 (Ib) NH2 (Ic)

  According to the invention, the polymer may be a homopolymer, in which case it consists only of one and the same siloxane repeating unit of formula (I).

  Such a homopolymer is, for example, a homopolymer formed by the repeating unit of formula (Ia).

  Alternatively, the polymer may also be a copolymer, in which case it may equally well consist of different siloxane repeating units all of the formula (I) that comprise one or more siloxane repeating units of formula (I) and one or more units repetitive others, siloxane or not.

  According to yet another preferred embodiment of the invention, the polymer is a copolymer which comprises two different siloxane repeating units, a first siloxane unit corresponding to formula (I) above in which X, Y, R1 and R2 have the same meaning as above, and a second siloxane unit of formula (III) below:

W

  + if o--) wherein W and Z, which may be the same or different, represent a hydrogen atom, a linear hydrocarbon group, branched or cyclic, saturated or unsaturated, having from 1 to 30 carbon atoms.

  Preferably, the second siloxane unit is a dihydrogensiloxane (W = Z = H), a methylhydrogensiloxane (one of W and Z = H, while the other = CH3) or a dimethylsiloxane (W = Z = CH3), the latter motif being preferred.

  Examples of such copolymers include copolymers comprising: a first siloxane unit of formula (Ia) and a second dimethylsiloxane unit; or - a first siloxane unit of formula (Ib) and a second dimethylsiloxane unit; or else - a first siloxane unit of formula (Ic) and a second dimethylsiloxane unit.

  According to the invention, these copolymers can be random, alternating or sequenced, but they are preferentially random.

  On the other hand, copolymers in which the first siloxane unit is, by number, about 47% of the repeating units forming these copolymers, are preferred, while the second siloxane unit is, in number, about 53% of the repeating units forming said copolymers.

  Whether it is a homopolymer or a copolymer, the molecular weight of the bulk polymer is generally greater than or equal to 200 g / mol, and is preferably 200 to 100,000 g / mol and, more preferably, from 1,000 to 10,000 g / mole.

  The polymer may also comprise a repeating unit derived from a monomer of the ethylene, propylene, ethylene oxide, styrene, vinyl carbazole or vinyl acetate type, capable of conferring on it higher mechanical properties, in particular in the case where it is desired to use it in the form of a thin film.

  According to yet another preferred embodiment of the invention, the polymer is in the form of a thin film which covers one or both sides of a suitably selected substrate depending on the physical property of the sensitive material whose variations are intended to be measured by this sensor.

  Alternatively, the polymer may also be in a massive form such as, for example, a cylinder having a certain porosity so as to make accessible to the nitro compounds all of the molecules forming said polymer.

  When in the form of a thin film, the latter preferably has a thickness of 10 Angstroms to 100 microns.

  Such a film may in particular be obtained by sputtering, spin-coating (spin coating) on the substrate of a solution containing the polymer, or dip-coating (dip coating) in the English language. -saxon) of the substrate in a solution containing the polymer.

  The substrate and the measuring system of the sensor are chosen according to the physical property of the polymer whose variations induced by the presence of nitro compounds are intended to be measured by the sensor.

  In this case, the polymer mass variations have proved particularly interesting to measure. Also, the sensor is preferably a gravimetric sensor.

  As examples of gravimetric sensors, mention may be made of sensors of the quartz microbalance type, the surface wave sensors, better known in the English terminology "SAW" for "Surface Acoustic Wave", such as Love wave sensors and Lamb wave sensors, as well as microleviers.

  Of the gravimetric sensors, quartz microbalance sensors are more particularly preferred. This type of sensor, whose operating principle has been described by Sanchez-Pedrono et al. in Anal. Chem. Acta, vol. 182, 1986, 285 [4], schematically comprises a piezoelectric substrate (or resonator), generally a quartz crystal covered on both sides with a metal layer, for example gold or platinum, serving as a 'electrode. The sensitive material covering one or both sides of the substrate, any mass variation of this material results in a variation of the vibration frequency of the substrate.

  Of course, it is also possible to use a polymer as defined above, as a sensitive material in sensors designed to measure variations of a physical property other than the mass such as, for example, resistive sensors based on the measurement of variations in electrical conductivity or optical sensors based on the measurement of fluorescence variations, luminescence, absorbance in the UV-visible range or wavelength in the infrared range.

  Indeed, although polymers comprising a siloxane repeating unit of formula (I) are not electrically conductive, they can be mixed with one or more conductive fillers to obtain composites having electrical conductivity suitable for use as materials. sensitive resistive sensors. These conductive fillers may be, for example, particles of carbon black or metal powders (Cu, Pd, Au, Pt, ...) or metal oxides (V2O3r TiO, ...).

  In the case of an optical sensor, it is possible either to exploit an intrinsic optical property of the polymer in the case where it has one (absorbance, IR spectrum, ...), or to give this polymer a particular optical property by coupling with a suitable marker, for example fluorescent or luminescent.

  The chemical sensor according to the invention can be integrated in a multisensor, that is to say in a device uniting a plurality of elementary sensors, these elementary sensors being able to be provided with sensitive materials, substrates and / or different measurement systems.

  Also, the invention relates to a multisensor comprising one or more elementary sensors assembled to each other and wherein at least one of these elementary sensors is a chemical sensor as defined above.

  The chemical sensors according to the invention have been found to have numerous advantages, in particular: an ability to specifically detect nitro compounds, and in particular nitroaromatic compounds, with high sensitivity since they are capable of detecting their presence in concentrations less than ppm (parts per million) and even to tenth of ppm, * speed of response and reproducibility of this response, * stability of performance over time and hence very good service life, to operate continuously, * a manufacturing cost compatible with a production of sensors in series, a very small amount of polymer (that is to say, in practice a few mg) being necessary for the manufacture of a sensor, and * The possibility of being miniaturized and, therefore, of being easily transportable and manipulable on all types of sites.

  The subject of the invention is also the use of a chemical sensor as defined above, for the detection or the determination of one or more nitro compounds, these compounds possibly being in solid, liquid or gaseous form (vapors ), but preferably being in gaseous form.

  According to the invention, the nitro compound (s) intended to be detected or assayed are chosen from nitroaromatic compounds, nitramines, nitrosamines and nitric esters.

  Examples of nitroaromatic compounds that may be mentioned include nitrobenzene, dinitrobenzene, trinitrobenzene, nitrotoluene, dinitrotoluene, trinitrotoluene, dinitrofluorobenzene, dinitrotrifluoromethoxybenzene, aminodinitrotoluene, dinitrotrifluoromethylbenzene, chlorodinitrotrifluoromethylbenzene, hexanitrosilbene or trinitrophenol (or picric acid).

  Nitramines are, for example, cyclotetramethylenetetranitramine (or octogen), cyclotrimethylenetrinitramine (or hexogen) and trinitrophenylmethylnitramine (or tetryl), while nitrosamines are, for example, nitrosodimethylamine.

  As for the nitric esters, it is, for example, pentrite, ethylene glycol dinitrate, diethylene glycol dinitrate, nitroglycerine or nitroguanidine.

  According to yet another preferred embodiment of the invention, the sensor is used for detecting or dosing explosives.

  The invention will be better understood in the light of the additional description, which relates to examples of preparation of aniline polysiloxanes capable of serving as sensitive materials in chemical sensors and to examples of embodiments of chemical sensors comprising such polysiloxanes. However, these examples are given only by way of illustration of the subject of the invention and do not constitute in any way a limitation of this object.

BRIEF DESCRIPTION OF THE DRAWINGS

  FIG. 1 represents the evolution of the quartz vibration frequency of a first example of a sensor according to the invention when this sensor is exposed to air and vapors of 2,4-dinitrotrifluoromethoxybenzene (DNTFMB).

  FIG. 2 represents the evolution of the quartz vibration frequency of a second example of a sensor according to the invention when this sensor is exposed to air and vapors of DNTFMB.

  FIG. 3 represents the evolution of the quartz vibration frequency of a third example of a sensor according to the invention when this sensor is exposed to air and vapors of DNTFMB, toluene, methyl ethyl ketone and ethanol.

  FIG. 4 represents the evolution of the quartz vibration frequency of a fourth example of a sensor according to the invention when this sensor is exposed to air and vapors of DNTFMB.

  FIG. 5 shows the quartz frequency variations of the second example of sensor according to the invention and of a sensor comprising Nallylaniline as a sensitive material when these sensors are exposed to DNTFMB on the day of their elaboration (OJ) and 28 days after (J28).

  FIG. 6 shows the evolution of the quartz vibration frequency of a fifth example of a sensor according to the invention when this sensor is exposed to air and vapors of dinitrotoluene (2,4-DNT).

  DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS Example 1 Preparation of aniline polysiloxanes Four polymers, designated respectively A, B, C and D, respectively, having the following compositions are prepared: Polymer A homopolymer of repeating unit of formula (Ia); Polymer B random copolymer formed from a repeating unit of formula (Ia) and a dimethylsiloxane repeating unit in a ratio of 0.47 unit of formula (Ia) for 0.53 dimethylsiloxane unit; Polymer C random copolymer formed of a repeating unit of formula (Ib) and a dimethylsiloxane repeating unit in a ratio of 0.47 unit of formula (Ib) for 0.53 dimethylsiloxane unit; Polymer D random copolymer formed by a repeating unit of formula (Ic) and a dimethylsiloxane repeating unit in a ratio of 0.47 unit of formula (Ic) for 0.53 dimethylsiloxane unit; by modifying polysiloxanes comprising, in the case of the preparation of polymer A, only a repeating unit methylhydrogensiloxane of formula (IV) below.

H

  and, in the case of the preparation of polymers B, C and D, a methylhydrogensiloxane repeating unit and a dimethylsiloxane repeating unit in a ratio of 0.47 methylhydrogensiloxane units per 0.53 dimethylsiloxane units.

  These polysiloxanes are especially available from ABCR under the references HMS 992 and HMS 501.

  The modification consists of a coupling of an allyl amino compound of formula (V) below: ## STR2 ## in which R represents one of the following groups: (IV) (V) NH 2 NH 2 on the repeating unit of formula (IV) by catalytic hydrosilylation according to the following reaction scheme:

R

H

I

  (Si-O + R - E- Si O) JH 3 / CH 3 This hydrosilylation is carried out in bulk for the polymers A and B, and in solution for the polymers C and D. In the case of the polymers A and B, the Allyl monomer (1.5 mmol of N-allylaniline, available from Sigma-Aldrich under the reference A2,900-3) is heated to 80 ° C under a stream of nitrogen.

  The catalyst (25 μl of hexachloroplatinic acid solution (H 2 PtCl 6), available from Sigma-Aldrich as 52,089-6, in 0.84 wt% isopropanol or 20 μl of Karstedt catalyst, available from Sigma-Aldrich under the reference 47,951-9) is added. After stirring for 15 minutes, the polysiloxane is added dropwise and the solution is heated at 105 ° C. for 5 hours. After filtration on activated charcoal, the product is purified by removing the volatiles by distillation under vacuum.

  (CH2) 3 The polymers A and B are thus obtained in the form of orange oils with a yield of 96% and 93%, respectively.

  In the case of polymers C and D, the allyl monomer (1.5 mmol of 4-amino-N-allylaniline, synthesized as described by Kaufman et al., Russian J.Org.Chem., Vol 37, 5, 2001, 707, [5], for polymer C, and 1.5 mmol of 2-allylaniline, synthesized as described by Tsuji et al., Chem Lett, 1995, 1121-1122, [6], for polymer D) in solution in 3 ml of toluene is heated at 80 ° C under a stream of nitrogen. The catalyst (0.84% by weight of H2PtC16 in solution in isopropanol or 20 μl of Karstedt catalyst) is added. After stirring for 15 minutes, the polysiloxane is added dropwise and the solution is heated at 105 ° C. for 5 hours. After filtration on activated charcoal, the product is purified by removing the volatiles by distillation under vacuum.

  The polymer C is thus obtained in the form of a black oil with a yield of 28%, and the polymer D in the form of a brown oil with a yield of 84%.

  EXAMPLE 2 Detection of DNTFMB by a Sensor According to the Invention In this example, a quartz microbalance sensor is made by covering on both sides an AT cut crystal, with a vibration frequency of 9 MHz, provided with two gold circular measuring electrodes (QA9RA-50 model, AMETEK PRECISION INSTRUMENTS), a B thin film of polymer B prepared according to Example 1.

  The deposition of this film is carried out by performing on each side of quartz 20 sprays of 0.3 seconds each of a solution of the polymer B in chloroform, of concentration equal to 5 g / l.

  The variation of the quartz vibration frequency due to this deposit is 9.9 kHz.

  The sensor is successively exposed to: air for 2100 seconds, DNTFMB at a concentration of 3 ppm in air for 600 seconds, and air E for 2310 seconds, air and DNTFMB. being at room temperature.

  Figure 1 illustrates the evolution of quartz vibration frequency during these exposures.

  In this figure, the curve A represents the values of the vibration frequency (F) of the quartz, expressed in Hz (hertz), as a function of time (t), expressed in seconds, while the curve B represents the values of the DNTFMB concentration ((Cl), expressed in ppm, also as a function of time.

  EXAMPLE 3 Detection of DNTFMB by a Sensor According to the Invention In this example, a quartz microbalance sensor is produced by covering the two faces of a quartz identical to that used in Example 2 of a thin film of the polymer. Prepared according to Example 1.

  The deposition of this film is carried out by performing on each side of quartz 8 sprays of 0.3 seconds each of a solution of the polymer A in chloroform, of concentration equal to 10 g / l.

  The variation of the quartz vibration frequency due to this deposit is 9.5 kHz.

  The sensor is successively exposed to: air for 460 seconds, DNTFMB E at a concentration of 3 ppm in air for 600 seconds, and air for 1800 seconds, air and DNTFMB being at ambient temperature.

  Figure 2 illustrates the evolution of quartz vibration frequency during these exposures.

  In this figure, the curve A represents the values of the quartz vibration frequency (F), expressed in Hz, as a function of time (t), expressed in seconds, while curve B represents the values of the DNTFMB concentration. ([C]), expressed in ppm, also as a function of time.

  EXAMPLE 4 Demonstration of the Selectivity of a Sensor According to the Invention for Nitrogen Compounds with Respect to Solvents In this example, a quartz microbalance sensor is made by covering the two faces of a quartz crystal. identical to that used in Example 2 of a thin film of the polymer C prepared in accordance with

Example 1

  The deposition of this film is carried out by performing on each side of quartz 23 sprays of 0.4 seconds each of a solution of the polymer C in chloroform, with a concentration of 5 g / l.

  The variation of the quartz vibration frequency due to this deposit is 10 kHz.

  The sensor is exposed successively to: de air for 1550 seconds, du DNTFMB at a concentration of 3 ppm in air for 600 seconds, É air for 1820 seconds, du DNTFMB at a concentration of 3 ppm in air for 600 seconds, É air for 1650 seconds, toluene at a concentration of 38,000 ppm in air for 600 seconds, air É for 130 seconds, É de la methyl ethyl ketone at a concentration of 126,000 ppm in air for 600 seconds, air for 170 seconds, ethanol at a concentration of 79,000 ppm in air for 170 seconds, and air for 50 seconds, air, DNTFMB, toluene, methyl ethyl ketone and ethanol being at room temperature.

  FIG. 3 represents the values of the quartz vibration frequency (F), expressed in Hz, as a function of time (t), expressed in seconds, the arrows f1 and f2 signaling the exposures to the DNTFMB, the arrow f3 the exposure with toluene, arrow f4 exposure to methyl ethyl ketone and arrow f5 that to ethanol.

  This figure shows that the exposure of the sensor according to the invention to solvents such as toluene, methyl ethyl ketone or ethanol, does not cause a sensor response comparable to that obtained when the latter is exposed to a nitrated compound.

  EXAMPLE 5 Detection of DNTFMB by a Sensor According to the Invention In this example, a quartz microbalance sensor is produced by covering on both sides a quartz identical to that used in Example 2 of a thin film of polymer D prepared according to

Example 1

  The deposition of this film is carried out by performing on each side of the quartz 16 sprays of 0.3 seconds each of a solution of the polymer D in chloroform, with a concentration of 5 g / l.

  The variation of the quartz vibration frequency due to this deposit is 10 kHz.

  The sensor is exposed successively to: air for 1224 seconds, DNTFMB at a concentration of 3 ppm in air for 600 seconds, air E for 1480 seconds, air and DNTFMB being at room temperature.

  Figure 4 illustrates the evolution of quartz vibration frequency during these exposures.

  In this figure, the curve A represents the values of the quartz vibration frequency (F), expressed in Hz, as a function of time (t), expressed in seconds, while curve B represents the values of the DNTFMB concentration. ([C]), expressed in ppm, also as a function of time.

  Example 6 Demonstration of the stability of the performances of a sensor according to the invention and of a sensor comprising N-allylaniline as sensitive material In this example, the performance of the sensor used in Example 3 is compared with those a sensor of identical structure but comprising, on each side, an N-allylaniline film in place of the polymer film B. The deposition of the N-allylaniline film is carried out by performing on each side of the quartz 12 sprays of 0.5 seconds each of a solution of this compound in chloroform, of concentration equal to 10 g / L, so as to lead to a variation of the quartz vibration frequency of 2 kHz.

  The two sensors are exposed for 10 minutes to DNTFMB, at a concentration of 3 ppm in air, the day of their elaboration (OJ) and 28 days after (D28). Between the two exposures, they are kept in the ambient air without any particular conditions.

  FIG. 5 shows the quartz frequency variations (AF), expressed in Hz, obtained for the two sensors at OJ and J28, those corresponding to the sensor according to the invention being represented in light gray and those corresponding to the sensor comprising N -allylaniline as a sensitive material being represented in dark gray.

  EXAMPLE 7 Detection of 2,4-DNT by a Sensor According to the Invention In this example, a quartz microbalance sensor is made by covering the two faces of a quartz identical to that used in Example 2 of a thin film of the polymer B prepared according to Example 1.

  The deposition of this film is carried out by performing on each side of the quartz 17 sprays of 0.3 seconds each of a solution of the polymer B in chloroform, of concentration equal to 10 g / l.

  The variation of the quartz vibration frequency due to this deposit is 9.9 kHz.

  The sensor is successively exposed to: air for 2450 seconds, 2,4-DNT at a concentration of 285 ppb in air for 600 seconds, and air for 350 seconds. air and 2,4-DNT being at room temperature.

  Figure 5 illustrates the evolution of quartz vibration frequency during these exposures.

  In this figure, the curve A represents the values of the vibration frequency (F) of the quartz, expressed in Hz, as a function of time (t), expressed in seconds, while the curve B represents the values of the concentration in 2 , 4-DNT ([C]), expressed in ppb, also as a function of time.

  Example 8 Comparison of the Performance of a Sensor According to the Invention and a Sensor Comprising a Thin Film of a Polysiloxane According to McGill et al (ibid)

  In this example, two quartz microbalance sensors are made, both comprising a quartz identical to that used in Example 2, but differing from each other in that the quartz of the first is covered on both sides. a thin film of the polymer B, while the quartz of the second is covered with a thin film of a polysiloxane having phenyl functional units substituted with two HFIP groups.

  This polysiloxane corresponds to the following formula (VI): ## STR3 ## The deposits of the films are made so that the variation of the frequency of the quartz vibration due to these deposits is equal to 10 kHz for each of the sensors.

  To do this, the deposition of the polymer film B is carried out by spraying a solution of the polymer B in chloroform, concentration of 5 g / l, on both sides of the sensor 20 times 0.3 seconds, while the deposition of the film of the polysiloxane of formula (VI) is carried out by spraying 30 times 0.2 seconds a solution of said polysiloxane in dichloromethane, of concentration equal to 2 g / L, on both sides of the quartz.

  The two sensors are exposed, under exactly the same conditions, to DNTFMB vapors of a concentration of 3 ppm at room temperature and for 10 minutes.

  The measurement of the quartz vibration frequency of the two sensors at the time to and at the time tiomin of this exposure gives a variation of the vibration frequency of 1 100 Hz for the quartz of the sensor according to the invention, and of 490 Hz - either more than 2 times lower - for the quartz of the sensor comprising the thin film of the polysiloxane of formula (VI).

REFERENCES CITED

  [1] Briglin et al., Proceedings of SPIE, vol. 4394, 2001, 912-921, [2] McGill et al., Sens. Actuators B65, 2000, 5-9, [3] POT WO-A-02/08314 [4] Sanchez-Pedrono et al., Anal. Chem. Acta, vol. 182, 1986, 285 [5] Kaufman et al., Russian J. Org. Chem., Vol. 37, 5, 2001, 707 [6] Tsuji et al., Chem. Lett., 1995, 1121-1122

Claims (24)

  A chemical sensor comprising, as a sensitive material, at least one polymer comprising a siloxane repeating unit which has the formula (I) below. R2 (I)   wherein: X and Y, which may be the same or different, represent a single bond or a linear, branched or cyclic, saturated or unsaturated hydrocarbon group comprising from 1 to 30 carbon atoms and optionally one or more heteroatoms and / or or a plurality of chemical functions comprising at least one heteroatom and / or one or more aromatic or heteroaromatic groups; R 1 represents an aniline group corresponding to formula (II) below: embedded image in which: Q represents a single bond, a group -CH 2 -, or a group -NR 3 in which R 3 represents a hydrogen atom or a hydrocarbon group linear, saturated or unsaturated, and comprising from 1 to 10 carbon atoms; R 4 to R 8, which may be identical or different, represent a hydrogen atom, a chemical function comprising at least one heteroatom, or a linear, branched or cyclic hydrocarbon group, saturated or unsaturated, comprising from 1 to 30 carbon atoms and optionally one or more heteroatoms and / or one or more chemical functions comprising at least one heteroatom and / or one or more aromatic or heteroaromatic groups; and wherein, when Q is a single bond or a -CH2- group, then at least one of R4 to R8 is -NR9R10 -amino in which R9 and R10 are independently of one another, a hydrogen atom, a chemical function comprising at least one heteroatom, or a linear, branched or cyclic hydrocarbon group, saturated or unsaturated, comprising from 1 to 30 carbon atoms and optionally one or more heteroatoms and / or one or more chemical functions comprising at least one heteroatom and / or one or more aromatic or heteroaromatic groups; R2 represents a hydrogen atom or an aniline group of formula (II) as defined above.   2. The sensor according to claim 1, wherein the siloxane repeating unit corresponds to formula (I) in which R1 represents a group of formula (IIa), (IIb) or (IIc) below: NH (IIb)   A sensor according to claim 1 or claim 2, wherein the siloxane repeating unit has the formula (I) wherein X is an alkylene group having 1 to 10 carbon atoms, Y is an alkylene group having 1 to 3 carbon atoms while R2 represents a hydrogen atom.   The sensor of claim 3, wherein the siloxane repeating unit has the formula (I) wherein X is propylene, Y is methylene, and R2 is hydrogen.   5. A sensor according to any one of the preceding claims wherein the siloxane repeating unit is one of the following formulas (Ia), (Ib) and (Ic): NH NH   (CH2) 3 (SiO) CH3 (Ia) (Ib) NH2 (CH2) 3 - (- SiO -) - CH3 (Ic) The sensor of any preceding claim, wherein the polymer is a homopolymer.   The sensor according to any one of claims 1 to 5, wherein the polymer is a copolymer which comprises two different siloxane repeating units, a first unit having the formula (I) wherein X, Y, R1 and R2 have the same same meaning as above, and a second ground corresponding to formula (III) below: W    (jSi o) Z (III) in which W and Z, which may be identical or different, represent a hydrogen atom, a hydrocarbon group, linear, branched or cyclic, saturated or unsaturated, comprising from 1 to 30 carbon atoms .   The sensor of claim 7, wherein the second siloxane unit is a dihydrogensiloxane unit, a methylhydrogensiloxane unit or a dimethylsiloxane unit.   9. The sensor of claim 6, wherein the polymer is a homopolymer consisting of the siloxane repeating unit of formula (Ia) below: The sensor of claim 8, wherein the polymer is a copolymer which comprises a first siloxane unit of formula (Ia) below. (Ia) NH   (CH2) 3 - (SiO) CH3 (Ia) and a second dimethylsiloxane unit.   The sensor of claim 8, wherein the polymer is a copolymer that comprises a first siloxane unit of formula (Ib) below: NH   (If O CH3 (Ib) and a second dimethylsiloxane unit.   The sensor of claim 8, wherein the polymer is a copolymer that comprises a first siloxane moiety of formula (Ic) below: and a second dimethylsiloxane moiety.   The sensor of any one of claims 10 to 12, wherein the copolymer is random, alternating or sequenced.   A sensor according to any one of claims 10 to 11, wherein the first repeating unit is, in number, about 47% of the repeating units forming the copolymer, while the second repeating unit is, in number, about 53% of the patterns forming the copolymer.   A sensor according to any one of the preceding claims, wherein the polymer or composite is present as a thin film covering one or both sides of a substrate.   The sensor of claim 15, wherein the thin film is from 10 angstroms to 100 microns thick. NH2 (Ic)   The sensor of any preceding claim which is a sensor is a gravimetric sensor.   18. Sensor according to any one of the preceding claims, which is a quartz microbalance sensor.   19. A multisensor comprising one or more elementary sensors assembled to each other and in which at least one of these elementary sensors is a chemical sensor according to any one of claims 1 to 18.   20. Use of a chemical sensor according to   any one of claims 1 to 18 or a   Multisensor according to Claim 19 for the detection or determination of one or more nitro compounds.   21. Use according to claim 20, wherein the one or more nitro compounds are chosen from nitroaromatic compounds, nitramines, nitrosamines and nitric esters.   22. Use according to claim 21, wherein the nitro compound (s) to be detected are in gaseous form.   23. Use according to any one of claims 20 to 22, wherein the one or more nitro compounds are chosen from nitrobenzene, dinitrobenzene, trinitrobenzene, nitrotoluene, dinitrotoluene, trinitrotoluene, dinitrofluorobenzene, dinitrotrifluoromethoxybenzene, 1 '. aminodinitrotoluene, dinitrotrifluoromethylbenzene, chlorodinitrotrifluoromethylbenzene, hexanitrostilbene, trinitrophenol, cyclotetramethylenetetranitramine, cyclotrimethylenetrinitramine, trinitrophenylmethylnitramine, nitrosodimethylamine, pentrite, ethylene glycol dinitrate, diethylene glycol dinitrate, nitroglycerine or nitroguanidine.   24. Use according to any one of claims 20 to 23 for the detection of explosives.